Drill grinder



Oct. 14, 1947. R. B. HANFORD I DRILL GRINDER Filed April 28, 1944 2 Sheets-Sheet 1 INVENTOR HAL PH 5. H/I/VFORD Oct. 14, 1947. R. B. HAN-FORD DRILL GRINDER Filed April 28, 1944 2 Sheets-Sheet 2 INVENTOR R/IL PH 5. HA/VFORD ATTORNEYS fw, hm, WMM cwpw.

Patented Oct. 14, 1947 UNITED STATES PATENT OFFICE 2,429,057 DRILL GRINDER a Ralph B. Hanford, Yonkers, N. Y. Application April 28, 1944, Serial No. 533,144

14 Claims.

This invention relates to drill grinders and especially those adapted to sharpen drills commonly known as twist drills.

Most devices or machines available for grinding or sharpening drills are expensive and are too' complicated for a layman to operate, or require considerable skill and mechanical aptitude in order to employ them in satisfactorily grinding and sharpening of a drill. The grinder of the present invention is extremely simple and cheap to manufacture, and yet all of the essential operations are substantially automatic, so that an amateur or novice can grind and sharpen drills satisfactorily with little or no experience.

Once a twist drill is correctly inserted in the drill holder of the drill grinder according to this invention, both sides orv lips of the point of the drill (if there be two) will automatically be ground to the correct angle, and simultaneously the correct clearance angle or depth of clearance of the lips will also be automatically ground. These and other advantages of: the present invention will be understood by consideration of the following specification taken together with the drawings, wherein: Fig. 1 is a side elevational view of a drill grinder according to the invention;

Fig. 2 is a second side elevational view of the same grinder with the drill holder rotated 90. with respect to the position illustrated in Fig. 1;

Fig. 3 is a .front elevational view of the drill grinder with the drill holder and certain associated parts shown in cross-section;

Fig. 4 is a sectional, view taken along line 4-4 of Fig. 2;

Fig. 5 is a sectional view taken along line 5-5 of Fig. 2;

Fig. 6 is a sectional view taken along line 3--6 of Fig. 2;

Fig. 7 is a sectional view taken along line 1-'l of Fig. 3; and V r Fig. 8 is an end view of the sharpened point of a two-lip twist drill such as-is illustrated in Figs. 1, 2 and 3. a V

Referring now to Figs. 1, 2 and 3, the drill grinder is shown as supported from a base I by a standard or supporting frame comprising a vertical post portion 2 and an offset arm portion In. In the illustrated embodiment this arm is oifset 31 from the vertical portion. Attached to and supported by vertical portion 2 of the standard is a grinding wheel 3 suitably driven 2 than would preferably be employed in practice. This wheel may be turned by hand or by power such as an electric motor, but the hand drive is simpler and cheaper and has proved satisfactory for the purposes intended.

The grinding wheel 3 together with its driving mechanism is adjustably supported on the vertical portion 2 of the standard, as shown in Figs. 1, 2 and 3, to permit vertical adjustment of the surface of the grinding wheel with respect to the point of a drill 35 when secured in the drill holder. The purpose of this adjustment will be explained later. Although such adjustment may be provided by any convenient means, the embodiment here illustrated comprises guide ways 6 on either side of the front of standard 2 in which a carriage 5 slides vertically. On this carriage is fastened the gear train 4 and the other parts of the grinding wheel mechanism. A bolt 8 passes through the carriage and through a vertical slot 43 in the standard 2. To the back of bolt 8 is fastened a wing nut I so that by tightening this wing nut the carriage 5 may be firmly secured at any desired point of vertical adjustment along standard 2.

' The drill holder consists of a hollow shaft it of which the lower exterior portion is threaded. Near the lower end of this threaded portion a double yoke-clamp or chuck supporting member 29 is secured. To this clamp is fastened a suitable drill-holding chuck, such a chuck being illustrated as including two opposed jaws 26 in which the drill 35 may be clamped. These chuck jaws are each pivoted to the ends of levers 28, as shown, and these levers in turn are pivoted intermediate their ends by pivots 21 to the clamp 29. The opposite ends of levers 28 are cut at an angle to provide cam faces or wedges 3| against which knurled ring I! engages. This ring is threaded to shaft l6 so that when the ring is rotated on the threads the edge of it engages wedges 3| tending to expand them, and this, in turn, urges the chuck jaws 26 toward each other to grip the drill 35. To automatically center the drill in the jaws it is desirable to form the inner surface of each in a V-shape, as shown in Fig. 6.

The chuck jaws 26 are guided so as to remain parallel and in correct alignment with each other. For this purpose a sleeve 34 is attached to the face of one jaw and a socket 33 is attached to the other. In socket 33 a pin 32 is secured, and this pin slides in sleeve 34, as shown in Figs. 1, 2 and 6, thus maintaining the face of the jaws parallel and in alignment at all positions thereof.

Th upper end of hollow shaft [6 is journaled in sleeve I2 so that it may slide longitudinally and rotate in sleeve I2. Beyond sleeve I2 a cap I8 is secured to the end of shaft I6. This cap may be secured to the shaft in any appropriate manner, a set screw I9 (Figs. 1 and 3) being here shown for that purpose. Cap I8 prevents the shaft I6 from sliding out through sleeve I2, but permits the required amount of longitudinal sliding for the purposes described below.

Attached to cap I8 are two oppositely disposed extensions, each carrying a cam follower 20 and I20 (Figs. 1 and '7). Cooperating with these cam followers is a cam 2I formed at the upper edge of sleev I2. In the embodiment illustrated this cam slopes from a. low point 23 I level with upper edge of sleeve I2, to a. high point 24 (Figs. 1 and 4). Thus counterclockwise rotation of the shaft I6 (looking downwardly toward the cap) while cam follower I20, for example, is held in contact with cam 2!, causes shaft IE to move upwardly in sleeve I2 a distance determined by the height of the cam.

When the shaft I6 rotated clockwise one of the followers and I29 will serve as a stop and strike against stop face 30, but when rotated counterclockwise the shaft IE will be drawn upwardly in sleeve I2 and dropped down again twice in each complete revolution.

For convenience in inserting a drill correctly in the chuck a latch is provided to lock the shaft I6 against movement both longitudinally and rotationally. This latch here takes the form of an arm hinged to sleeve I2 and shaped to engage a slot 22 in cam follower I20. Thus the arm 25 itself prevents rotation of shaft I6 and the heel 44 formed at the head of arm 25 engages the top of the cam follower holding the follower against the cam and preventing it, together with shaft I5 from sliding longitudinally.

Sleeve I2 is hinged to a U-shaped bracket I5 which, in turn, is secured to arm It) of the standard. The hinge between bracket II and sleeve I2 comprises a screw [4 provided with a wing nut I5. By this means the lower end of the chuck may be swung in an arc toward and away from the grinding surface of the wheel, and, if desired, may be clamped in any position by tightening wing nut I5.

The swinging movement of the drill holder, and thus of the end of the chuck, in a direction toward the grinding surface of the wheel 3 can be adjusted and set by means of a stop screw 39 which passes through a threaded hole in arm I0 and terminates near one end of an extension of sleeve I2 forming a stop face 38 (Figs. 1 and 4). locking it in any desired position by means of lock nut 45, the angle which the longitudinal axis of the drill makes with respect'to the grinding surface of thewheel 3 as the chuck is swung toward the wheel can be adjusted over a considerable range. This angle is that to which the drill point is to be finally ground, and for usual purposes is 59, as is shown in Fig. '1. It is convenient to mark a scale of angles on the side of bracket II which cooperates with an index marked or formed. on the side-of sleeve 25 to indicate the angle at which the drill is to b ground.

Bracket II is secured-to arm III by means of two screws 40 and 4| as shown in Figs.' 1 and 3. These screws pass through arm IE) and each carries a nut on the inside of the bracket. It is preferable that the'hole in "the bracket through Thus by turning stop screw 39 and 4 which lower screw 4| passes be cut in the form of a slot as shown in Fig. 3, so that the entire drill holder may be swung slightly sideways as viewed from the front in Fig. 3. The angle A of this offset, as shown in Fig. 3 may be, say 2 or 3 and should be in the direction or rotation of the wheel. This angle of offset of the longitudinal axis of the drill from the center of the grinding wheel eliminates any tendency toward chattering.

The drill point A correctly sharpened drill point of a twist drill is shown in Fig. 8. From the illustration it will be seen that the point comprises two straight cutting edges 36 and 36a. These cutting edges are not radial but are parallel with each other, separated by a small distance, which is the thickness of the web of the drill. These cutting edges should be groundto exactly the same length and make exactly the same angle with the axis of the drill, the proper angle being 59 for usual purposes. Hence, usually, the index 46 (Fig. 1) would always be set at 59, although the drilling extremely soft material, the angle would best be less, and for extremely hard material the angle would best be greater than 59.

As in a chisel or other cutting tool, there must be a clearance behind the cutting edge to permit the drill to cut. The, material of the drill between the cutting edge 36 and heel point 31 is known as the cutting lip. Ina two-lip twist drill each cutting lip comprises a sector of approximately degrees... It is this lip which must be ground away more toward the back or heel than at the cutting edge to provide the necessary clearance. The'angle formed by grinding the necessary depth of clearance in the standard drill is 12, but. occasionally is between 12 and 15. If the clearance angle is ground the same for both cutting lips, as should be the case, the heel points 3 and. 31a will be on a straight line passing through the center of the drill, as shown in Fig. 8. To attain this uniformity by hand grinding is extremely difiicult, and is rarely achieved by skilled machinists. The drill grinder of the present invention automatically grinds the correct clearance angle equally on both cutting lips by operation of the cam 2| and followers 20 and I20 which move the drill point away from the grinding surface of the grindingwheel in the direction of the longitudinal axis of the drill at a predetermined rate" and for a predetermined distance as the drill is rotated. If it be desired to construct the grinder so that different clearance angles may be included, the positions of the cam and cam followers may be interchanged. Then, if a different clearance angle, say 15", be required, cap I8 with its "12 cams may be removed and another cap with the 15 cams may be substituted. 'Also, other forms of caps having more or less than two cams may be employed for grinding. drills having more or less than two cutting lips- Operation The fOl'lOWiIlg description of the manner of use and operation of the drill grinder in accordance with this invention will make clear the extremely simple manner in which even-a novice may grind a correctly shaped point one drill. For convenience, the grinding. wheel mechanism may first be dropped to the. bottom of its adjustment in the standard by loosening wing nut -1, Stop screw 39 having previously been adjusted so that index 46 indicates the correct angle of grind (say 59), wing nut I4 is loosened slightly to enable the operatorto' swing the drill holder upward away from grinding wheel 3. Latch 25 is then closed so as to lock the chuck against movement in any direction. When so locked the chuck is in the position shown in Fig. 3, except that it would be swung upward away from the grinding wheel. The chuck is then opened by unscrewing knurled ring l1, and the drill 35 to be sharpened is inserted between the jaws 26 in such position that an imaginary line drawn through heel points 31 and 31a (Fig. 8) is parallel to the lower edge 46 on the flat surface of jaws 26, as illustrated in Fig. 1. These heel points can be readily lined up with the lower edges 46'of jaws 26 by sighting along the axis of the drill, preferably from the point end. The drill will then be in correct angular alignment with respect to the grinding surface of the grinding wheel provided the remaining parts of the device are correctly related to each other, as mentioned in the last paragraph of this specification. V

The entire grinder having first been secured to a suitable support and the drill having been firmly clamped in the chuck in the correctly alignedinitial position, the drill holder should be swung downwardlytoward the surface of the grinding wheel against stop 38. The grinding wheel mechanism is then slid upwardly in standard 2 until the surface of the wheel swings the drill on pivot l4 upwardly a couple of degrees. The grinding wheel mechanism is now clamped in this position by tightening wing nut 1, Next the latch 25 is disengaged, as shown in Fig. 2, and the chuck is turned about 90, clockwise looking downwardly at the cap l8, until one of the cam followers 2!], I strikes stop face 36. Then, the operator turns the grinding wheel with one hand while he rotates the entire chuck mechanism and drill with the other hand by rotating the knurled ring I1 counterclockwise, at the same time pressing the drill point firmly against the surface of the grinding wheel. The two operations'of turning the grinding wheel and alternately rotating the drill clockwise and counterclockwise while pressing it against the grinding surface should be repeated until one lip of the drill point has been ground away as much as may be in view of the adjustments previously made. This will result in the final angle of the cutting edge in relation to the axis of the drill being that set by screw 39 against stop 38.

Secondly, without changin any adjustments whatever the shaft 16 is rotated 180 in sleeve 12 so that the opposite cam follower engages stop face 30, and the above-described grinding operation is repeated in respect to the second cutting lip. After the second cutting lip has been ground as much as may be in view of the previously made adjustments, the drill oint will have been correctly ground and the drill may conveniently be removed by swinging the chuck upwardly and unscrewing ring I 1.

In order to distribute the wear on the surface of the grinding whee1 3 it is preferable to insert the drills in the chuck so that they extend from the chuck different lengths in different instances. These different lengths are compensated for by raising the grinding wheel mechanism the correct distance, as above explained.

It will be noted that the drill grinder in accordance with this invention performs the grinding operation in substantially the reverse order to 6. that commonly followed in grinding drills by hand and heretofore customarily employed by drill-grinding machines. In other words, the drill grinder of the present invention begins grinding the cutting lip at the heel 3'! (Fig. 8) and finishes the grinding at cutting edge 36, which is the last portion of the cutting lip to be in contact with the Wheel as the drill point is drawn away from the surface of the grinding wheel by the cam action above described,

It is important, in order to grind the drill point so that the cutting edges 36 and 36a are parallel, as explained above under Operation, that the several components of the mechanism including the cam or cams, the cam followers, the chuck, the alignment of the drill therein, the offset angle A (Fig. 3), should be originally designed so as to be correctly related to each other. This relation should be such that as the cutting edge 36 is being ground, viz., just as it is leaving contact with the surface of the grinding wheel, the line 36 should be parallel to the axis of the grinding wheel. Otherwise the cutting edges 36 and 36a will either diverge or conver e toward the axis of the drill which would result in an incorrectly ground drill point.

What is claimed is:

l. Ina drill grinder, the combination which comprises: a vertical standard having a base; a grinding wheel secured to said standard with its axis of rotation perpendicular to the vertical axis of said standard; means for adjusting said wheel on said standard vertically with respect to said base; an arm secured to the top of said standard ofiset with respect to said vertical axis and slanting away from said wheel; a drill holder including a drill-holding chuck, a shaft to the lower portion of which said chuck is secured, and a sleeve in which the upper portion of said shaft is slidably and rotatably journaled; pivot means secured to the upper portion of said arm and to said sleeve whereby the lower end of said chuck may be swung in an arc toward and away from the. grinding surface of said wheel; cam and follower means se cured to said sleeve and said shaft for automatically moving said chuck away from said grinding surface in the direction of the longitudinal axis of said shaft as said shaft is rotated on said lastmentioned axis; a stop mechanically associated with said arm and cooperating with a part of said pivot means for limiting the swing of said holder toward said grinding surface, and stop means associated with said cam for limiting the rotation of said shaft in one direction only.

2. In a drill grinder, the combination which comprises: a vertical standard having a base; a

grinding whee1 secured to said standard with its axis of rotation perpendicular to the vertical axis of said standard; an arm secured to the top of said standard offset with respect to said vertical axis and slanting away from said wheel; a drill holder including a drill-holding chuck, a shaft to the lower portion of which said chuck is secured, and a sleeve in which the upper portion of said shaft is slidably and rotatably journaled; pivot means secured to the upper portion of said arm and to said sleeve whereby the lower end of said chuck may be swung in an arc toward and away from the grinding surface of said Wheel; cam and follower means secured to said sleeve and said shaft for automatically moving said chuck away from said grinding surface in the direction of the longitudinal axis of said shaft as said shaft is rotated on said last-mentioned axis; a stop mechanically associated with said arm and co0per-..

ating with a part of said pivot means for limiting the swing of said holder toward said grinding surface, stop means associated with said cam' for limiting the rotation of said shaft in one direction only; and means for adjusting the spacing between said chuck and said wheel when said holder is swung against said stop.

3. In a drill grinder, the combination which comprises: a vertical standard having a base; a grinding wheel secured to said standard with its axis of rotation perpendicular to the vertical axis of said standard; an arm secured to the top of said standard offset with respect to said vertical axis and slanting away from said wheel; a drill holder including a drill-holding chuck, a shaft to the lower portion of which said chuck is secured, and a sleeve in which the upper portion of said shaft is slidably and rotatably journaled; the longitudinal axis of said shaft being offset in the direction of rotation of said wheel'by a small angle with respect to the vertical plane containing the axis of rotation of said wheel; pivot means secured to the upper portion of said arm and to said sleeve whereby the lower end of said chuck may be swung in an arc toward and away from the grinding surface ofsaid wheel; cam and follower means secured to said sleeve and said shaft for automatically moving said chuck away from said grinding surface in the direction of thelongitudinal axis of said shaft as said shaft is rotated on said last-mentioned axis, a stop mechanically as sociated with said arm and cooperating with a part of said pivot means for limiting the swing of said holder toward said grinding surface; stop means associated with said cam for limiting the rotation of said shaft in one direction only; and means for adjusting the spacing between said chuck and said wheel when said holder is swung against said stop.

4:. In a drill grinder, the combination which comprises: a vertical standard having a base; a grinding wheel secured to said standard with its axis of rotation perpendicular to the vertical axis of said standard; an arm secured to the top of said standard offset with respect to said vertical axis and slanting away from said wheel; a drill holder including a drill-holding chuck, a Shaft to the lower portionof which said chuck is secured, and a sleeve in which the'upper portion of said shaft is slidably and rotatably journaled; means mechanically associated with said arm for ad.- justing the angle of inclination of the longitudinal axis of said shaft with respect to the vertical plane containing the axis of rotation of said wheel; pivot means secured to the upper portion of said arm and to said sleeve whereby the lower end of said chuck may be swung in an arc toward and away from the grinding surface of said wheel; cam and follower mean-s secured to said sleeve and said shaft for automatically moving said chuck away from said grinding 'surface in the direction of the longitudinal axis of said shaft as said shaft is rotated on said last-mentioned axis; a stop mechanically associated with said arm and cooperating with a. part of said pivot means for limiting the swing of said ho-ldertoward said grinding surface; stop means associated with said cam for limiting the rotation of said shaft in one direction only; and means for adjusting the spacing between said chuck and said wheel when said holder is swung against said stop.

5. In a drill grinder, the combination which comprises: a vertical standard having a base; a grinding wheel securedito said standard with its axis of rotation perpendicular to the vertical axis of said standard; an arm secured to the top of said standard offset with respect to said vertical axis and slanting away from said wheel; a drill holder including a drill-holding chuck, a shaft to the lower portion of which said chuck is secured, and a sleeve in which the upper portion of said shaft is slidably and rotatably journaled; pivot means secured to the upper portion of said arm and to said sleeve whereby the lower end of said chuck may be swung in an arc toward and away from the grinding surface of said wheel, cam and follower means secured to said sleeve and said shaft for automatically moving said chuck away from said grinding surface in the direction of the longitudinal axis of said shaft as said shaft is rotated on said last-mentioned axis; an adjustable stop mechanically associated with said arm and cooperating with a part of said pivot means for adjustably limiting the swing of said holder toward said grinding surface; stop means associated with said cam for limiting the rotation of said shaft in one direction only; and means for adjusting the spacing between said chuck and said wheel when said holder is swung against said adjustable stop.

6. In a drill grinder; a base and a standard extending therefrom; a grinding wheel supported from said base; a sleeve connected to the standard above the grinding wheel for pivotal adjustment in a vertical plane; means for adjusting the spacing between said wheel and said holder; a shaft rotatable and axially slidable in the sleeve and having portions projecting above and below the sleeve, said portion projecting below the sleeve being threaded and having a chucksupporting member secured to the lower end thereof; a drill-holdin chuck having levers respectively pivoted intermediate their lengths at diametricallyopposite points on said chuck-supporting member, and opposing jaws respectively pivoted to the lower ends of said levers and adapt-' ed to retain a drill therebetween, the upper ends of said levers having opposing cam faces; and an internally threaded member adjustable on the threaded projecting portion of said shaft op erable to spread said cam faces and cause said jaws to clamp the drill; aligning means respectively connected to said jaws for maintaining parallel alignment of said jaws; the portion of said shaft projecting above said sleeve having a cap for preventing said shaft from sliding out of the sleeve but permitting some axial displacement of the shaft; said cap having secured thereto diametrically opposed cam followers; and a cam surface on said sleev for cooperating with said cam followers and having low and high points arranged so that counterclockwise rotation of the cap and shaft as viewed looking down upon the cap causes upward movement of the shaft and clockwise rotation thereof causes a follower to strike against a stop face adjacent the high point of the cam surface, whereby said drillholding chuck is drawn upwardly and dropped twice in each revolution in a counterclockwise direction and prohibited against axial displacement when rotated in the clockwise direction.

7. A drill grinder of the type defined in claim 6, wherein one of said cam followers on the shaft has a slot, and a latch is hinged to the sleeve and shaped to engage the'sides of said slot and an upper surface of said follower to lock the shaft against both rotational and axial movement at times when the drill is being inserted between the chuckjaws.

8. In a drill grinder, the combination with a base, of a rotatable grinding wheel having a grinding surface, means for supporting said wheel above said base, a standard secured to said base, a shaft,sleeve means pivotally secured to'said standard'for supporting said shaft upon said standard, said shaft being rotatable and axially slidable in said sleeve means, a drill-holding chuck secured to said shaft, a guide edge on said chuck in relation to which a drill to be secured in said chuck may be aligned, a first stop means fixed to'said shaft, a second stop means fixed to saidsleeve means cooperating with said first stop means to'prevent rotation of said shaft in one direction only while permitting continuous rotation of said shaft in the other direction, said first stop means and said guide edge both being secured to said shaft in fixed angular relationship with respect to each other irrespective of the operation of said chuck and in ad justable relationship to said second stop means, whereby when the drill is inserted in the chuck so that a line through the heel points of said drill is parallel with said guide surface and the shaft is rotated so that said first and second stop means are in contact, the drill will be automatically presented to said grinding surface in correct angular alignment for grinding, a cam and a cam follower, one of which is carried by said sleeve and the other by the shaft, said cam and cam follower being constructed and arranged to cause the drill-holding chuck to slide longitudinally relative to the sleeve means and to move away from the grinding wheel as the drill-holding chuck is rotated in one direction.

9. In a drill grinder, the combination with a rotatable grinding wheel having a grinding surface, a base, means supporting said wheel above said base, a standard secured to said base, a shaft, sleeve means secured to'said standard for supporting said shaft on said standard, said shaft being rotatable and axially slidable in said sleeve means, a drill-holding chuck secured to said shaft, a guide surface on said chuck in relation to which a drill to be secured in said chuck may be aligned, and means effectively on said shaft and said sleeve means for locking said shaft against rotational and axial movement in said sleeve means, of means to facilitate the aligning and securing of a drill in said chuck, comprising a first stop means fixed to said shaft and a second stop means fixed to said sleeve means, said first and second stop means cooperating to prevent rotation of said shaft in one direction only, said first stop means and said guide surface both being secured to said shaft in fixed angular relationship with respect to each other irrespective of the operation of said chuck and in adjustable relationship to said second stop means, whereby when the drill is inserted in said chuck so that a line through the heel points of said drill is parallel with said guide surface and the shaft is rotated until said first and second stop means are in contact, the drill will be automatically presented to said grinding surface in correct angular alignment for grinding.

10. In a drill grinder, the combination which comprises: a base; a standard attached to said base; a grinding wheel rotatably supported on said standard above said base and having a grinding surface; a drill holder; said drill holder and said grinding wheel being mounted for relative spacial adjustment; said drill holder including a shaft, a drill-holding chuck secured to the lower end of said shaft, a sleeve in which the shaft 10 is slidably and rotatably journalled, and pivot means securing the sleeve to said standard whereby said chuck may be, swung in an arc toward and away from the grinding surface of said wheel so that a drill in said holder may be presented to said grinding surface at any desired grinding angle; cam and follower means, one each being secured to said sleeve and said shaft for automatically moving said chuck away from said grinding surface in the direction of the longitudinal axis of said shaft as said shaft is rotated in one direction on said last-mentioned axis, means for effecting relative spacial adjustment between the drill holder and the grinding surface on said wheel to permit selection of initial location of the drill on said grinding surface, adjustable means attached to said standard for limiting the pivotal movement of said dril1 holder toward said grinding surfaceto adjustably predetermine the final ground angle of the drill point, and stop means effectively secured to said sleeve and said shaft for limiting the rotation of said shaft over a predetermined angle in one direction only while permitting continuous rotation of said shaft in the other direction.

11. In a drill-point grinder, a standard, a grinding wheel rotatably supported with respect to said standard, a sleeve connected to the standard above the grinding wheel for pivotal movement in a vertical plane, a drill holder journaled in said sleeve for slidable and rotary movements, a cam and a cam follower, one of which is carried by said sleeve and the other by the drill holder, said cam and cam follower being constructed and arranged to cause the drill holder to slide longitudinally relative to the sleeve and to move away from the grinding wheel as the drill holder is rotated in one direction, said cam and cam follower having cooperating stop faces to positively limit rotation of the drill holder in one direction while permitting continuous rotation of the drill holder in the other direction, and a stop on said standard against which said sleeve is adapted to abut to limit the swing thereof towards said grinding wheel to predetermine the final angle with respect to the axis at which the point of a drill held in said drill holder is ground,

12. In a drill-point grinder, a standard, a grinding wheel rotatably supported with respect to said standard, a sleeve connected to the standard above the grinding wheel for pivotal movement in a vertical plane, a drill holder journaled in said sleeve for slidable and rotary movements, a cam and a cam follower, one of which is carried by said sleeve and the other by the drill holder, said cam and cam follower bein constructed and arranged to cause the drill holder to slide longitudinally relative to the sleeve and to move away from the grinding wheel as the drill holder is rotated in one direction, said cam and cam follower having cooperating stop faces to positively limit rotation of the drill holder in one direction while permitting continuous rotation of the drill holder in the other direction, said cooperating stop faces limiting rotation of the drill holder in said one direction to equal sectors, whereby automatically to grind different lips of a drill held in said drill holder equally, and a stop on said standard against which said sleeve is adapted to abut to limit the swing thereof towards said grinding wheel to predetermine the final angle with respect to the axis at which the point of a drill held in said drill holder is ground.

13. In a drill-point grinder, a standard, a grinding wheel rotatably supported with respect to said standard, a, sleeve connected to the standard above the grinding wheel for pivotal movement in a vertical plane, a drill holder journaled in said sleeve for slidable and rotary movements, a cam and a cam follower, one of which is carried by said sleeve and the other by the drill holder, said cam and cam follower being constructed and arranged to cause the drill holder to slide longitudinally relative to the sleeve and to move away from the grinding wheel as the drill holder is rotated in one direction, said cam and cam follower having cooperating stop faces to positively limit rotation of the drill holder in one direction while permitting continuous rotation of the drill holder in the other direction, said cooperating stop faces limiting rotation of the drill holder in said one direction to two equal sectors of approximately 90 degrees each whereby automatically to grind two different lips of a drill held in said drill holder equally, and a stop on said standard against which said sleeve is adapted to abut to limit the swing thereof towards said grinding wheel to predetermine the final angle with respect to the axis at which the point of a drill held in said drill holder is ground.

14. In a drill-point grinder, a standard, a grinding wheel rotatably supported with respect to said standard, a sleeve connected to the standard above the grinding wheel for pivotal movement in a vertical plane, a drill holder journaled in said sleeve for slidable and rotary movements, a cam and a cam follower, one of which is carried by said sleeve and the other by the drill holder, said cam and cam follower being constructed and ar- 12 ranged to cause the drill holder to slide longitudinally relative to the sleeve and to move away from the grinding wheel as the drill holder is rotated in one direction, said cam and cam follower having cooperating stop faces to positively limit rotation of the drill holder in one direction while permitting continuous rotation of the drill holder in the other direction, and two stop means disposed at approximately degrees radially with respect to the axis of a drill in said drill holder, each serving asa guide from which to commence grindin a different lip of a drill point, a stop on said standard against which said sleeve is adapted to abut to limit the swing thereof towards said grinding wheel to predetermine the final angle with respect to the axis at which the point of a drill held in said drill holder is ground.

I RALPH B. I-IANFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 390,223 Gasiorowski Oct. 2, 1888 1,698,807 Willhauck -4 Jan. 15, 1929 Re. 20,491 Weishampel Aug. 31, 1937 2,344,420 Schwartz Mar. 14, 1944 FOREIGN PATENTS Number Country Date 385,746 Great Britain Jan. 5, 1933 Certificate of Correction Patent No. 2,429,057. October 14, 1947.

RALPH B. HANFORD It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 4, line 6, for direction or read direction of line 25, for the read for; line 47, after achieved insert except; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 6th day of January, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

